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An androgen (from Greek ''andr-'', the stem of the word meaning "man") is any natural or synthetic
steroid hormone A steroid hormone is a steroid , hypothetical a steroid with 32 carbon atoms. Its core ring system (ABCD), composed of 17 carbon atoms, is shown with IUPAC The International Union of Pure and Applied Chemistry (IUPAC ) is an international ...
that regulates the development and maintenance of male characteristics in
vertebrate Vertebrates () comprise all species of animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consume organic ma ...
s by binding to
androgen receptor The androgen receptor (AR), also known as NR3C4 (nuclear receptor subfamily 3, group C, member 4), is a type of nuclear receptor In the field of molecular biology, nuclear receptors are a class of proteins found within cells that are responsi ...

androgen receptor
s. This includes the embryological development of the primary
male sex organs A sex organ (or reproductive organ) is any part of an animal or plant that is involved in sexual reproduction Sexual reproduction is a type of reproduction Reproduction (or procreation or breeding) is the biological process by which new in ...
, and the development of male
secondary sex characteristic Secondary sex characteristics are features that appear during puberty Puberty is the process of physical changes through which a child Biologically, a child (plural children) is a human Humans (''Homo sapiens'') are the most populo ...
s at
puberty Puberty is the process of physical changes through which a child Biologically, a child (plural children) is a human Humans (''Homo sapiens'') are the most abundant and widespread species In biology Biology is the natur ...

puberty
. Androgens are synthesized in the
testes Testicle or testis (plural testes) is the male Male (symbol: ♂) is the sex of an organism that produces the gamete (sex cell) known as sperm, which fuses with the larger female gamete, or ovum, in the process of fertilization. A male or ...

testes
, the
ovaries The ovary is an organ found in the female reproductive system 300px, 1. Labia_majora.html"_;"title="Vulva: 2. Labia_majora">Vulva: 2. Labia_majora; 3. Labia_minora; 4. Vulval_vestibule.html" "title="Labia_minora.html ...

ovaries
, and the
adrenal glands The adrenal glands (also known as suprarenal glands) are endocrine glands that produce a variety of hormones including adrenaline and the steroids aldosterone and cortisol. They are found above the kidneys. Each gland has an outer cortex wh ...

adrenal glands
. Androgens increase in both males and females during puberty. The major androgen in males is
testosterone Testosterone is the primary sex hormone and anabolic steroid in males. In humans, testosterone plays a key role in the development of Male reproductive system, male reproductive tissues such as testes and prostate, as well as promoting secondar ...
.
Dihydrotestosterone Dihydrotestosterone (DHT, 5α-dihydrotestosterone, 5α-DHT, androstanolone or stanolone) is an endogenous Endogenous substances and processes are those that originate from within a system such as an organism, Tissue (biology), tissue, or Cell ...
(DHT)
androstenedione Androstenedione, or 4-androstenedione (abbreviated as A4 or Δ4-dione), also known as androst-4-ene-3,17-dione, is an endogenous weak androgen An androgen (from Greek ''andr-'', the stem of the word meaning "man") is any natural or syntheti ...

androstenedione
are of equal importance in male development. DHT ''in utero'' causes differentiation of penis, scrotum and prostate. In adulthood, DHT contributes to balding, prostate growth, and
sebaceous gland A sebaceous gland is a microscopic exocrine Exocrine glands are gland In animals, a gland is a group of cells in an animal's body that synthesizes substances (such as hormone A hormone (from the Greek participle , "setting in motion") is a ...
activity. Although androgens are commonly thought of only as male
sex hormones Sex hormones, also known as sex steroids, gonadocorticoids and gonadal steroids, are steroid hormone A steroid hormone is a steroid that acts as a hormone. Steroid hormones can be grouped into two classes: corticosteroids (typically made in the ...
, females also have them, but at lower levels: they function in
libido Libido (; colloquial Colloquialism or colloquial language is the style (sociolinguistics), linguistic style used for casual (informal) communication. It is the most common functional style of speech, the idiom normally employed in conversation ...
and
sexual arousal Sexual arousal (also sexual excitement) is typically the arousal Arousal is the physiological and psychological Psychology is the science of mind and behavior. Psychology includes the study of consciousness, conscious and Unconscio ...
. Also, androgens are the precursors to
estrogen Estrogens or oestrogens, are a class of natural or synthetic s responsible for the development and regulation of the female and s. There are three major estrogens that have estrogenic hormonal activity: (E1), (E2), and (E3). Estradiol, an ...

estrogen
s in both men and women. In addition to their role as natural hormones, androgens are used as
medication A medication (also called medicament, medicine, pharmaceutical drug, medicinal drug or simply drug) is a drug used to medical diagnosis, diagnose, cure, therapy, treat, or preventive medicine, prevent disease. Drug therapy (pharmacotherapy) ...

medication
s; for information on androgens as medications, see the
androgen replacement therapy Androgen replacement therapy (ART), often referred to as testosterone replacement therapy (TRT), is a form of hormone therapy in which androgens, often testosterone, are replaced. ART is often prescribed to counter the effects of male hypogona ...
and
anabolic steroid Anabolic steroids, also known more properly as anabolic–androgenic steroids (AAS), are steroid A steroid is a biologically active organic compound In , organic compounds are generally any s that contain - . Due to carbon's ability t ...
articles.


Types and examples

The main subset of androgens, known as adrenal androgens, is composed of 19-carbon steroids synthesized in the
zona reticularis The zona reticularis (sometimes, reticulate zone) is the innermost layer of the adrenal cortex The adrenal cortex is the outer region and also the largest part of an adrenal gland. It is divided into three separate zones: zona glomerulosa, zona f ...
, the innermost layer of the
adrenal cortex The adrenal cortex is the outer region and also the largest part of an adrenal gland. It is divided into three separate zones: zona glomerulosa, zona fasciculata and zona reticularis. Each zone is responsible for producing specific hormones. It is a ...
. Adrenal androgens function as weak steroids (though some are precursors), and the subset includes
dehydroepiandrosterone Dehydroepiandrosterone (DHEA), also known as androstenolone, is an endogenous Endogenous substances and processes are those that originate from within a system such as an organism, Tissue (biology), tissue, or Cell (biology), cell. Endogenous ...

dehydroepiandrosterone
(DHEA), dehydroepiandrosterone sulfate (DHEA-S),
androstenedione Androstenedione, or 4-androstenedione (abbreviated as A4 or Δ4-dione), also known as androst-4-ene-3,17-dione, is an endogenous weak androgen An androgen (from Greek ''andr-'', the stem of the word meaning "man") is any natural or syntheti ...

androstenedione
(A4), and
androstenediol Androstenediol, or 5-androstenediol (abbreviated as A5 or Δ5-diol), also known as androst-5-ene-3β,17β-diol, is an endogenous weak androgen An androgen (from Greek ''andr-'', the stem of the word meaning "man") is any natural or synthetic ...
(A5). Besides testosterone, other androgens include: * Dehydroepiandrosterone (DHEA) is a steroid hormone produced in the adrenal cortex from
cholesterol Cholesterol is any of a class of certain organic compound, organic molecules. A cholesterol is a sterol (or chemical modification, modified steroid), a type of lipid. Cholesterol is biosynthesis, biosynthesized by all animal Cell (biology)#Euk ...

cholesterol
. It is the primary precursor of natural estrogens. DHEA is also called dehydroisoandrosterone or dehydroandrosterone. * Androstenedione (A4) is an androgenic steroid produced by the
testes Testicle or testis (plural testes) is the male Male (symbol: ♂) is the sex of an organism that produces the gamete (sex cell) known as sperm, which fuses with the larger female gamete, or ovum, in the process of fertilization. A male or ...

testes
, adrenal cortex, and
ovaries The ovary is an organ found in the female reproductive system 300px, 1. Labia_majora.html"_;"title="Vulva: 2. Labia_majora">Vulva: 2. Labia_majora; 3. Labia_minora; 4. Vulval_vestibule.html" "title="Labia_minora.html ...

ovaries
. While androstenediones are converted metabolically to
testosterone Testosterone is the primary sex hormone and anabolic steroid in males. In humans, testosterone plays a key role in the development of Male reproductive system, male reproductive tissues such as testes and prostate, as well as promoting secondar ...
and other androgens, they are also the parent structure of
estrone Estrone (E1), also spelled oestrone, is a steroid, a weak estrogen, and a minor female sex hormone. It is one of three major endogenous estrogens, the others being estradiol and estriol. Estrone, as well as the other estrogens, are biosynthesis, ...

estrone
. Use of androstenedione as an athletic or
bodybuilding supplement Bodybuilding supplements are dietary supplements commonly used by those involved in bodybuilding, weightlifting, mixed martial arts, and athletics for the purpose of facilitating an increase in lean body mass. The intent is to increase muscle, ...
has been banned by the
International Olympic Committee The International Olympic Committee (IOC; french: Comité international olympique, ''CIO'') is a non-governmental sports organisation based in Lausanne , neighboring_municipalities= Bottens Bottens is a municipalities of Switzerland, m ...
, as well as other sporting organizations. *
Androstenediol Androstenediol, or 5-androstenediol (abbreviated as A5 or Δ5-diol), also known as androst-5-ene-3β,17β-diol, is an endogenous weak androgen An androgen (from Greek ''andr-'', the stem of the word meaning "man") is any natural or synthetic ...
(A5) is the steroid
metabolite In biochemistry Biochemistry or biological chemistry, is the study of chemical process In a scientific Science (from the Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-Europ ...
thought to act as the main regulator of
gonadotropin Gonadotropins are glycoprotein hormones secreted by gonadotropic cells of the anterior pituitary A major Organ (anatomy), organ of the endocrine system, the anterior pituitary (also called the adenohypophysis or pars anterior) is the glandular ...
secretion. *
Androsterone Androsterone, or 3α-hydroxy-5α-androstan-17-one, is an endogenous steroid hormone A steroid hormone is a steroid that acts as a hormone. Steroid hormones can be grouped into two classes: corticosteroids (typically made in the adrenal cortex, ...

Androsterone
is a chemical byproduct created during the breakdown of androgens, or derived from
progesterone Progesterone (P4) is an endogenous Endogenous substances and processes are those that originate from within a system such as an organism, Tissue (biology), tissue, or Cell (biology), cell. Endogenous substances and processes contrast with exo ...

progesterone
, that also exerts minor masculinising effects, but with one-seventh the intensity of testosterone. It is found in approximately equal amounts in the
plasma Plasma or plasm may refer to: Science * Plasma (physics), one of the four fundamental states of matter * Plasma (mineral) or heliotrope, a mineral aggregate * Quark–gluon plasma, a state of matter in quantum chromodynamics Biology * Blood plasma ...
and
urine Urine is a liquid by-product A by-product or byproduct is a secondary product derived from a production process, process or ; it is not the primary product or service being produced. A by-product can be useful and marketable or it can be cons ...

urine
of both males and females. *
Dihydrotestosterone Dihydrotestosterone (DHT, 5α-dihydrotestosterone, 5α-DHT, androstanolone or stanolone) is an endogenous Endogenous substances and processes are those that originate from within a system such as an organism, Tissue (biology), tissue, or Cell ...
(DHT) is a metabolite of testosterone, and a more potent androgen than testosterone in that it binds more strongly to androgen receptors. It is produced in the skin and reproductive tissue. Determined by consideration of all biological assay methods (circa 1970):''Steroid Biochemistry and Pharmacology'' by Briggs and Brotherton, Academic Press.


Female ovarian and adrenal androgen

Ovaries and adrenal gland produce much lower levels than the testes. Regarding the relative contributions of ovaries and adrenal gland to female androgen levels, in a study with six menstruating women the following observations have been made: * Adrenal contribution to peripheral T, DHT, A, DHEA and DHEA-S is relatively constant throughout the menstrual cycle * Ovarian contribution of peripheral T, A and DHEA-S reaches maximum levels at midcycle, whereas ovarian contribution to peripheral DHT and DHEA does not seem to be influenced by the menstrual cycle * Ovary and adrenal cortex contribute equally to peripheral T, DHT and A. With the exception that at midcycle ovarian contribution of peripheral A is twice that of the adrenal. * Peripheral DHEA and DHEA-S are produced mainly in the adrenal cortex which provides 80% of DHEA and over 90% of DHEA-S.


Biological function


Male prenatal development


Testes formation

During mammalian development, the gonads are at first capable of becoming either
ovaries The ovary is an organ found in the female reproductive system 300px, 1. Labia_majora.html"_;"title="Vulva: 2. Labia_majora">Vulva: 2. Labia_majora; 3. Labia_minora; 4. Vulval_vestibule.html" "title="Labia_minora.html ...

ovaries
or testes. In humans, starting at about week 4, the gonadal rudiments are present within the
intermediate mesoderm Intermediate mesoderm or intermediate mesenchyme is a narrow section of the mesoderm (one of the three primary germ layers) located between the paraxial mesoderm and the lateral plate of the developing embryo. The intermediate mesoderm develops in ...

intermediate mesoderm
adjacent to the developing kidneys. At about week 6, epithelial
sex cords In embryogenesis, the sex cords, (primitive sex cords or gonadal cords) are structures that develop from the gonadal ridges. After sexual differentiation, at day 49, the sex cords in male Male (♂) is the sex of an organism that produces the ...
develop within the forming testes and incorporate the
germ cell A germ cell is any biological cell The cell (from Latin ''cella'', meaning "small room") is the basic structural, functional, and biological unit of all known organisms. Cells are the smallest units of life, and hence are often referred to a ...
s as they migrate into the gonads. In males, certain
Y chromosome The Y chromosome is one of two sex chromosome A chromosome is a long DNA molecule with part or all of the genome, genetic material of an organism. Most eukaryotic chromosomes include packaging proteins called histones which, aided by Chaper ...
genes, particularly
SRY Testis-determining factor (TDF), also known as sex-determining region Y (SRY) protein, is a DNA-binding protein protein complex with DNA s (blue). These proteins' basic amino acids bind to the acidic phosphate groups on DNA. repressor heli ...
, control development of the male phenotype, including conversion of the early bipotential gonad into testes. In males, the sex cords fully invade the developing gonads.


Androgen production

The mesoderm-derived
epithelial Epithelium is one of the four basic types of animal Tissue (biology), tissue, along with connective tissue, muscle tissue and nervous tissue. It is a thin, continuous, protective layer of compactly packed Cell (biology), cells with little Ext ...
cells of the sex cords in developing testes become the Sertoli cells, which will function to support sperm cell formation. A minor population of nonepithelial cells appear between the tubules by week 8 of human fetal development. These are Leydig cells. Soon after they differentiate, Leydig cells begin to produce androgens.


Androgen effects

The androgens function as
paracrineParacrine signaling is form of cell signaling or cell-to-cell communication in which a cell produces a signal to induce changes in nearby cells, altering the behaviour of those cells. Signaling molecules known as paracrine factors diffuse over a rel ...
hormone A hormone (from the Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is appr ...

hormone
s required by the Sertoli cells to support sperm production. They are also required for masculinization of the developing male fetus (including penis and scrotum formation). Under the influence of androgens, remnants of the mesonephron, the Wolffian ducts, develop into the
epididymis The epididymis (; plural: epididymides or ) is a tube that connects a testicle Testicle or testis (plural testes) is the male Male (symbol: ♂) is the sex of an organism that produces the gamete (sex cell) known as sperm, which fuses w ...

epididymis
,
vas deferens The vas deferens, or ductus deferens, is part of the male reproductive system The male reproductive system consists of a number of sex organs that play a role in the process of human reproduction. These organs are located on the outside of the ...

vas deferens
and
seminal vesicles The seminal vesicles (also called vesicular glands, or seminal glands), are a pair of two convoluted tubular glands that lie behind the urinary bladder The urinary bladder, or simply bladder, is a hollow muscular organ in humans and other ver ...

seminal vesicles
. This action of androgens is supported by a hormone from Sertoli cells, Müllerian inhibitory hormone (MIH), which prevents the embryonic Müllerian ducts from developing into fallopian tubes and other female reproductive tract tissues in male embryos. MIH and androgens cooperate to allow for movement of testes into the scrotum.


Early regulation

Before the production of the pituitary hormone
luteinizing hormone Luteinizing hormone (LH, also known as lutropin and sometimes lutrophin) is a hormone A hormone (from the Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic R ...
(LH) by the embryo starting at about weeks 11–12,
human chorionic gonadotrophin Human chorionic gonadotropin (hCG) is a hormone for the maternal recognition of pregnancy produced by trophoblast cells that are surrounding a growing embryo (syncytiotrophoblast initially), which eventually forms the placenta after implantation (h ...
(hCG) promotes the differentiation of Leydig cells and their production of androgens at week 8. Androgen action in target tissues often involves conversion of testosterone to 5α-
dihydrotestosterone Dihydrotestosterone (DHT, 5α-dihydrotestosterone, 5α-DHT, androstanolone or stanolone) is an endogenous Endogenous substances and processes are those that originate from within a system such as an organism, Tissue (biology), tissue, or Cell ...
(DHT).


Male pubertal development

At the time of
puberty Puberty is the process of physical changes through which a child Biologically, a child (plural children) is a human Humans (''Homo sapiens'') are the most abundant and widespread species In biology Biology is the natur ...

puberty
, androgen levels increase dramatically in males, and androgens mediate the development of masculine
secondary sexual characteristic Secondary sex characteristics are features that appear during puberty in human Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedality, bipedalism and large, complex brains. This has ena ...
s as well as the activation of
spermatogenesis Spermatogenesis is the process by which haploid spermatozoa develop from germ cells in the seminiferous tubules of the testis. This process starts with the Mitosis, mitotic division of the stem cells located close to the basement membrane of the ...

spermatogenesis
and
fertility Fertility is the capability to produce offspring through reproduction following the onset of sexual maturity. The fertility rate is the average number of children born by a female during her lifetime and is quantified Demography, demographicall ...
and masculine behavioral changes such as
gynephilia Androphilia and gynephilia are terms used in behavioral science to describe sexual orientation, as an alternative to a gender binary homosexual and heterosexual conceptualization. Androphilia describes sexual attraction to men or masculinity; gyne ...
and increased
sex drive Libido (; colloquial: sex drive) is a person's overall sexual drive or desire for sexual activity. In psychoanalytic theory libido is psychic drive or energy, particularly associated with sexual instinct, but also present in other instinctive ...

sex drive
. Masculine secondary sexual characteristics include
androgenic hair Body hair, or androgenic hair, is the terminal hair that develops on the human body during and after puberty. It is differentiated from the head hair and less visible vellus hair, which is much finer and lighter in color. The growth of androgenic ...

androgenic hair
,
voice deepening A hoarse voice, also known as dysphonia or hoarseness, is when the voice involuntarily sounds breathy, raspy, or strained, or is softer in volume or lower in pitch. A hoarse voice, can be associated with a feeling of unease or scratchiness in the t ...
, emergence of the
Adam's apple The Adam's apple or laryngeal prominence, is the lump or protrusion in the human neck The neck is the part of the body on many vertebrate Vertebrates () comprise all species of animal Animals (also called Metazoa) are multicellular ...
, broadening of the shoulders, increased
muscle mass Skeletal muscles (commonly referred to as muscles) are organs An organ is a group of tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. A given organ's tissues can be broadly cate ...
, and penile growth.


Spermatogenesis

During puberty, androgen, LH and
follicle stimulating hormone Follicle-stimulating hormone (FSH) is a gonadotropin Gonadotropins are glycoprotein hormones secreted by gonadotropic cells of the anterior pituitary A major Organ (anatomy), organ of the endocrine system, the anterior pituitary (also call ...
(FSH) production increase and the sex cords hollow out, forming the seminiferous tubules, and the germ cells start to differentiate into sperm. Throughout adulthood, androgens and FSH cooperatively act on Sertoli cells in the testes to support sperm production. Exogenous androgen supplements can be used as a
male contraceptive Male contraceptives, also known as male birth control, are methods of preventing pregnancy that solely involve the male physiology. The most common kinds of male contraception include condoms, outercourse, and vasectomy. In domestic animals, cast ...
. Elevated androgen levels caused by use of androgen supplements can inhibit production of LH and block production of endogenous androgens by Leydig cells. Without the locally high levels of androgens in testes due to androgen production by Leydig cells, the seminiferous tubules can degenerate, resulting in infertility. For this reason, many transdermal androgen patches are applied to the scrotum.


Fat deposition

Males typically have less body fat than females. Recent results indicate androgens inhibit the ability of some fat cells to store lipids by blocking a signal transduction pathway that normally supports adipocyte function. Also, androgens, but not estrogens, increase beta
adrenergic receptor The adrenergic receptors or adrenoceptors are a class of G protein-coupled receptor G protein-coupled receptors (GPCRs), also known as seven-(pass)-transmembrane domain receptors, 7TM receptors, heptahelical receptors, serpentine receptors, and ...
s while decreasing alpha adrenergic receptors- which results in increased levels of epinephrine/ norepinephrine due to lack of alpha-2 receptor negative feedback and decreased fat accumulation due to epinephrine/ norepinephrine then acting on lipolysis-inducing beta receptors.


Muscle mass

Males typically have more
skeletal muscle Skeletal muscles (commonly referred to as muscles) are Organ (biology), organs of the vertebrate muscular system that are mostly attached by tendons to bones of the skeleton. The muscle cells of skeletal muscles are much longer than in the other ...

skeletal muscle
mass than females. Androgens promote the enlargement of skeletal muscle cells and probably act in a coordinated manner to function by acting on several cell types in skeletal muscle tissue. One cell type conveys hormone signals to generating muscle, the
myoblast Myogenesis is the formation of skeletal muscle, skeletal muscular tissue, particularly during embryonic development. Skeletal muscle#Skeletal muscle fibers, Muscle fibers generally form through the fusion of precursor cell, precursor myoblasts int ...
. Higher androgen levels lead to increased expression of androgen receptor. Fusion of myoblasts generates myotubes, in a process linked to androgen receptor levels.


Brain

Circulating levels of androgens can influence human behavior because some
neuron A neuron or nerve cell is an electrically excitable cell that communicates with other cells via specialized connections called synapse In the nervous system In biology Biology is the natural science that studies life and living ...

neuron
s are sensitive to steroid hormones. Androgen levels have been implicated in the regulation of human
aggression Aggression is overt or covert, often harmful, social interaction with the intention of inflicting damage or other harm upon another individual. It may occur either reactively or without provocation. In humans, aggression can be caused by various ...
and libido. Indeed, androgens are capable of altering the structure of the brain in several species, including mice, rats, and primates, producing
sex differences Sexual dimorphism is the condition where the two sexes of the same species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A spec ...
. Numerous reports have shown androgens alone are capable of altering the structure of the brain, but identification of which alterations in neuroanatomy stem from androgens or estrogens is difficult, because of their potential for conversion. Evidence from
neurogenesis Neurogenesis is the process by which nervous system In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, m ...
(formation of new neurons) studies on male rats has shown that the
hippocampus The hippocampus (via Latin from Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its popul ...

hippocampus
is a useful brain region to examine when determining the effects of androgens on behavior. To examine
neurogenesis Neurogenesis is the process by which nervous system In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, m ...
, wild-type male rats were compared with male rats that had testicular feminization mutation (TMF), a
genetic disorder A genetic disorder is a health problem caused by one or more abnormalities in the genome In the fields of molecular biology Molecular biology is the branch of biology Biology is the natural science that studies life and li ...
resulting in complete or partial insensitivity to androgens and a lack of external
male genitalia Male ( ♂) is the sex of an organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any individual contiguous system that embodies the Life#Biology, properties of life. It is a synonym for ...

male genitalia
. Neural injections of were applied to males of both groups to test for
neurogenesis Neurogenesis is the process by which nervous system In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, m ...
. Analysis showed that
testosterone Testosterone is the primary sex hormone and anabolic steroid in males. In humans, testosterone plays a key role in the development of Male reproductive system, male reproductive tissues such as testes and prostate, as well as promoting secondar ...
and
dihydrotestosterone Dihydrotestosterone (DHT, 5α-dihydrotestosterone, 5α-DHT, androstanolone or stanolone) is an endogenous Endogenous substances and processes are those that originate from within a system such as an organism, Tissue (biology), tissue, or Cell ...
regulated adult
hippocampal The hippocampus (via Latin from Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its popul ...
neurogenesis Neurogenesis is the process by which nervous system In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, m ...
(AHN). Adult
hippocampal The hippocampus (via Latin from Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its popul ...
neurogenesis Neurogenesis is the process by which nervous system In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, m ...
was regulated through the
androgen receptor The androgen receptor (AR), also known as NR3C4 (nuclear receptor subfamily 3, group C, member 4), is a type of nuclear receptor In the field of molecular biology, nuclear receptors are a class of proteins found within cells that are responsi ...

androgen receptor
in the wild-type male rats, but not in the TMF male rats. To further test the role of activated
androgen receptors The androgen receptor (AR), also known as NR3C4 (nuclear receptor subfamily 3, group C, member 4), is a type of nuclear receptor of a heterodimer of the nuclear receptors PPAR-γ (green) and Retinoid X receptor alpha, RXR-α (cyan) bound to doub ...
on AHN, , an
antiandrogen Antiandrogens, also known as androgen antagonists or testosterone blockers, are a class of drug File:Aspirine macro shot.jpg, Uncoated aspirin Tablet (pharmacy), tablets, consisting of about 90% acetylsalicylic acid, along with a minor amount o ...
drug that competes with
testosterone Testosterone is the primary sex hormone and anabolic steroid in males. In humans, testosterone plays a key role in the development of Male reproductive system, male reproductive tissues such as testes and prostate, as well as promoting secondar ...
and
dihydrotestosterone Dihydrotestosterone (DHT, 5α-dihydrotestosterone, 5α-DHT, androstanolone or stanolone) is an endogenous Endogenous substances and processes are those that originate from within a system such as an organism, Tissue (biology), tissue, or Cell ...
for
androgen receptors The androgen receptor (AR), also known as NR3C4 (nuclear receptor subfamily 3, group C, member 4), is a type of nuclear receptor of a heterodimer of the nuclear receptors PPAR-γ (green) and Retinoid X receptor alpha, RXR-α (cyan) bound to doub ...
, and
dihydrotestosterone Dihydrotestosterone (DHT, 5α-dihydrotestosterone, 5α-DHT, androstanolone or stanolone) is an endogenous Endogenous substances and processes are those that originate from within a system such as an organism, Tissue (biology), tissue, or Cell ...
were administered to normal male rats.
Dihydrotestosterone Dihydrotestosterone (DHT, 5α-dihydrotestosterone, 5α-DHT, androstanolone or stanolone) is an endogenous Endogenous substances and processes are those that originate from within a system such as an organism, Tissue (biology), tissue, or Cell ...
increased the number of
BrdU Bromodeoxyuridine (5-bromo-2'-deoxyuridine, BrdU, BUdR, BrdUrd, broxuridine) is a synthetic nucleoside analogue Nucleoside analogues are nucleosides which contain a nucleic acid analogue and a sugar. Nucleotide analogs are nucleotide Nucle ...
cells, while inhibited these cells. Moreover, estrogens had no effect. This research demonstrates how androgens can increase AHN. Researchers also examined how mild exercise affected androgen synthesis which in turn causes AHN activation of N-methyl-D-aspartate (NMDA) receptors.
NMDA ''N''-Methyl--aspartic acid or ''N''-Methyl--aspartate (NMDA) is an amino acid Amino acids are organic compound , CH4; is among the simplest organic compounds. In chemistry, organic compounds are generally any chemical compounds that con ...

NMDA
induces a calcium flux that allows for synaptic plasticity which is crucial for AHN. Researchers injected both orchidectomized (ORX) (castrated) and sham castrated male rats with
BrdU Bromodeoxyuridine (5-bromo-2'-deoxyuridine, BrdU, BUdR, BrdUrd, broxuridine) is a synthetic nucleoside analogue Nucleoside analogues are nucleosides which contain a nucleic acid analogue and a sugar. Nucleotide analogs are nucleotide Nucle ...
to determine if the number of new cells was increased. They found that AHN in male rats is increased with mild exercise by boosting synthesis of
dihydrotestosterone Dihydrotestosterone (DHT, 5α-dihydrotestosterone, 5α-DHT, androstanolone or stanolone) is an endogenous Endogenous substances and processes are those that originate from within a system such as an organism, Tissue (biology), tissue, or Cell ...
in the
hippocampus The hippocampus (via Latin from Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its popul ...

hippocampus
. Again it was noted that AHN was not increase via activation of the
estrogen receptor Estrogen receptors (ERs) are a group of proteins found inside cell (biology), cells. They are receptor (biochemistry), receptors that are activated by the hormone estrogen (17β-estradiol). Two classes of ER exist: nuclear estrogen receptors (ER ...
s. Androgen regulation decreases the likelihood of
depression Depression may refer to: Mental health * Depression (mood), a state of low mood and aversion to activity * Mood disorders characterized by depression are commonly referred to as simply ''depression'', including: ** Dysthymia ** Major depressive ...
in males. In
preadolescent Preadolescence, also commonly known as pre-teen, is a stage of Human development (biology), human development following early childhood and preceding adolescence.New Oxford American Dictionary. 2nd Edition. 2005. Oxford University Press. It commo ...
male rats,
neonatal An infant (from the Latin word ''infans'', meaning 'unable to speak' or 'speechless') is the more formal or specialised synonym for the common term ''baby'', meaning the Offspring, very young offspring of human beings. The term may also b ...
rats treated with developed more depression-like symptoms compared to control rats. Again
BrdU Bromodeoxyuridine (5-bromo-2'-deoxyuridine, BrdU, BUdR, BrdUrd, broxuridine) is a synthetic nucleoside analogue Nucleoside analogues are nucleosides which contain a nucleic acid analogue and a sugar. Nucleotide analogs are nucleotide Nucle ...
was injected into both groups of rats in order to see if cells were multiplying in the living tissue. These results demonstrate how the organization of androgens has a positive effect on
preadolescent Preadolescence, also commonly known as pre-teen, is a stage of Human development (biology), human development following early childhood and preceding adolescence.New Oxford American Dictionary. 2nd Edition. 2005. Oxford University Press. It commo ...
hippocampal The hippocampus (via Latin from Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its popul ...
neurogenesis Neurogenesis is the process by which nervous system In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, m ...
that may be linked with lower depression-like symptoms.
Social isolation Social isolation is a state of complete or near-complete lack of contact between an individual and society A society is a group A group is a number A number is a mathematical object used to counting, count, measurement, measure, an ...
has a hindering effect in AHN whereas normal regulation of androgens increases AHN. A study using male rats showed that
testosterone Testosterone is the primary sex hormone and anabolic steroid in males. In humans, testosterone plays a key role in the development of Male reproductive system, male reproductive tissues such as testes and prostate, as well as promoting secondar ...
may block
social isolation Social isolation is a state of complete or near-complete lack of contact between an individual and society A society is a group A group is a number A number is a mathematical object used to counting, count, measurement, measure, an ...
, which results in
hippocampal The hippocampus (via Latin from Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its popul ...
neurogenesis Neurogenesis is the process by which nervous system In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, m ...
reaching
homeostasis In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanis ...
—regulation that keeps internal conditions stable. A
Brdu Bromodeoxyuridine (5-bromo-2'-deoxyuridine, BrdU, BUdR, BrdUrd, broxuridine) is a synthetic nucleoside analogue Nucleoside analogues are nucleosides which contain a nucleic acid analogue and a sugar. Nucleotide analogs are nucleotide Nucle ...
analysis showed that excess
testosterone Testosterone is the primary sex hormone and anabolic steroid in males. In humans, testosterone plays a key role in the development of Male reproductive system, male reproductive tissues such as testes and prostate, as well as promoting secondar ...
did not increase this blocking effect against
social isolation Social isolation is a state of complete or near-complete lack of contact between an individual and society A society is a group A group is a number A number is a mathematical object used to counting, count, measurement, measure, an ...
; that is, the natural circulating levels of androgens cancel out the negative effects of
social isolation Social isolation is a state of complete or near-complete lack of contact between an individual and society A society is a group A group is a number A number is a mathematical object used to counting, count, measurement, measure, an ...
on AHN.


Female-specific effects

Androgens have potential roles in relaxation of the
myometrium The myometrium is the middle layer of the uterine wall, consisting mainly of uterine smooth muscle cells (also called uterine myocytes) but also of supporting stromal and vascular tissue. Its main function is to induce uterine contractions. Struc ...
via non-genomic,
androgen receptor The androgen receptor (AR), also known as NR3C4 (nuclear receptor subfamily 3, group C, member 4), is a type of nuclear receptor In the field of molecular biology, nuclear receptors are a class of proteins found within cells that are responsi ...

androgen receptor
-independent pathways, preventing premature
uterine contractionA uterine contraction is a muscle contraction of the uterine smooth muscle. Throughout menstrual cycle The uterus frequently contracts throughout the entire menstrual cycle, and these contractions have been termed ''endometrial waves'' or ''contr ...
s in pregnancy.


Androgen insensitivity

Reduced ability of an XY-
karyotype A karyotype is a preparation of the complete set of metaphase Metaphase () is a stage of mitosis In cell biology Cell biology (also cellular biology or cytology) is a branch of biology Biology is the natural science that studies ...

karyotype
fetus to respond to androgens can result in one of several conditions, including infertility and several forms of
intersex Intersex people are individuals born with any of several sex characteristics Sexual characteristics are physical or behavioral traits of an organism (typically of a sexually dimorphic organism) which are indicative of its biological sex. Th ...
conditions.


Miscellaneous

Yolk androgen levels in certain birds have been positively correlated to social dominance later in life. See
American coot The American coot (''Fulica americana''), also known as a mud hen or pouldeau, is a bird of the family (biology), family Rallidae. Though commonly mistaken for ducks, American coots are only distantly related to ducks, belonging to a separate ord ...

American coot
.


Biological activity

Androgens bind to and activate
androgen receptor The androgen receptor (AR), also known as NR3C4 (nuclear receptor subfamily 3, group C, member 4), is a type of nuclear receptor In the field of molecular biology, nuclear receptors are a class of proteins found within cells that are responsi ...

androgen receptor
s (ARs) to mediate most of their
biological effect In evolutionary biology Evolutionary biology is the subfield of biology that studies the evolution, evolutionary processes (natural selection, common descent, speciation) that produced the Biodiversity, diversity of life on Earth. In the 1930s, ...
s.


Relative potency

Determined by consideration of all biological assay methods (circa 1970): 5α-Dihydrotestosterone (DHT) was 2.4 times more potent than testosterone at maintaining normal prostate weight and duct lumen mass (this is a measure of epithelial cell function stimulation). Whereas DHT was equally potent as testosterone at preventing prostate cell death after castration.


Non-genomic actions

Androgens have also been found to signal through
membrane androgen receptor Membrane androgen receptors (mARs) are a group of G protein-coupled receptors (GPCRs) which bind and are activated by testosterone and/or other androgens. Unlike the androgen receptor (AR), a nuclear receptor which mediates its effects via genome, g ...
s, which are distinct from the classical nuclear androgen receptor.


Biochemistry


Biosynthesis

Androgens are
synthesized Synthesis or synthesize may also refer to: Science Chemistry and biochemistry *Chemical synthesis, the execution of chemical reactions to form a more complex molecule from chemical precursors **Organic synthesis, the chemical synthesis of or ...

synthesized
from
cholesterol Cholesterol is any of a class of certain organic compound, organic molecules. A cholesterol is a sterol (or chemical modification, modified steroid), a type of lipid. Cholesterol is biosynthesis, biosynthesized by all animal Cell (biology)#Euk ...

cholesterol
and are produced primarily in the
gonad A gonad, sex gland, or reproductive gland is a mixed gland that produces the gametes (sex cells) and sex hormones of an organism. In the female of the species the reproductive cells are the egg cells, and in the male the reproductive cells are t ...
s (testicles and ovaries) and also in the
adrenal gland The adrenal glands (also known as suprarenal glands) are endocrine gland Endocrine glands are ductless glands of the endocrine system The endocrine system is a messenger system comprising feedback loops of the hormones released by interna ...

adrenal gland
s. The testicles produce a much higher quantity than the ovaries. Conversion of testosterone to the more potent DHT occurs in
prostate gland The prostate is both an accessory gland of the male reproductive system and a muscle-driven mechanical switch between urination and ejaculation. It is found only in some mammals. It differs between species anatomically, chemically, and physio ...
,
liver The liver is an organ Organ may refer to: Biology * Organ (anatomy) An organ is a group of Tissue (biology), tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. A given organ's t ...

liver
,
brain A brain is an organ Organ may refer to: Biology * Organ (anatomy) An organ is a group of Tissue (biology), tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. A given organ's tis ...

brain
and skin.


Metabolism

Androgens are
metabolized Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life Life is a characteristic that distinguishes physical entities A bubble of exhaled gas in water In common usage and classical mechanics, a phys ...

metabolized
mainly in the
liver The liver is an organ Organ may refer to: Biology * Organ (anatomy) An organ is a group of Tissue (biology), tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. A given organ's t ...

liver
.


Medical uses

A low testosterone level (hypogonadism) in men may be treated with testosterone administration. Prostate cancer may be treated by removing the major source of testosterone: testicle removal (
orchiectomy Orchiectomy (also named orchidectomy, and sometimes shortened as orchi) is a surgery, surgical procedure in which one or both testicles are removed. The surgery is performed as treatment for testicular cancer, as part of Sex reassignment surgery ...
); or agents which block androgens from accessing their receptor:
antiandrogen Antiandrogens, also known as androgen antagonists or testosterone blockers, are a class of drug File:Aspirine macro shot.jpg, Uncoated aspirin Tablet (pharmacy), tablets, consisting of about 90% acetylsalicylic acid, along with a minor amount o ...
s.


See also

*
Andrology Andrology (from grc, ἀνήρ, ''anēr'', genitive In grammar In linguistics, the grammar (from Ancient Greek ''grammatikḗ'') of a natural language is its set of structure, structural constraints on speakers' or writers' composition of c ...
*
Endocrine system The endocrine system is a messenger system comprising feedback loops of the hormone A hormone (from the Greek participle , "setting in motion") is any member of a class of signaling molecules in multicellular organisms, that are transported ...

Endocrine system
* Exercise and androgen levels *
Androgen insensitivity syndrome Androgen insensitivity syndrome (AIS) is an intersex condition with an estimated prevalence of about 1:20,000-64,000 in XY (chromosomally male) births, resulting in the partial or complete inability of the Animal cell, cell to respond to androgens. ...
* Testosterone and the cardiovascular system * List of steroid abbreviations * List of androgens/anabolic steroids * List of androgens/anabolic steroids available in the United States


References

{{Authority control Androgens and anabolic steroids, Hepatotoxins Hormones of the hypothalamus-pituitary-gonad axis Sex hormones